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Research for a university project about seaweed resulted in a woman stumbling upon a method to harness the power of satellite imagery to detect plastic pollution in the ocean. In 2018, Lauren Biermann was scouring a satellite image of the ocean off the coast of the Isle of May, Scotland, searching for signs of floating seaweed for a project at her university. Her eyes were drawn to lines of white dots gently curving along an ocean front.

“It was weird because I was seeing floating things that didn’t look like plants, and I didn’t know what they could be,” Biermann, an Earth observation scientist at Plymouth Marine Laboratory in the U.K., told Mongabay. She said she considered the fact that it could be plastic, but found it hard to believe that Scotland had patches of plastic off its coast. “I spent the first three months trying to prove that it wasn’t plastic, so I went and made a library of all of the things floating, like foam and driftwood.”

During her investigation, Biermann came across a project conducted by the University of the Aegean in Greece, in which a team of academic staff and students used drone and satellite image technology to identify “plastic targets,” such as water bottles, plastic bags and fishing nets, on the sea surface. This data helped Biermann connect the dots in her own research.

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satellite imagery plastic pollution
Satellite view of plastic in ocean near Scotland. Image by Lauren Biermann.

“I went, yes, okay, this is plastic,” Biermann said. “It was the first time I had … data to validate what I had seen in Scotland, and that’s how I could build a spectral signature of plastic, and then go and apply it to other places.”

More than 8.3 billion tons of plastic waste enter the oceans each year, equivalent to a garbage truck dumping its contents into the sea every minute of the day, according to a report by the World Economic Forum. Anything more than 5 millimeters in size, about a fifth of an inch, is generally considered to be “macroplastic,” while anything below that size is “microplastic.”

Biermann and a team of colleagues embarked on their own study of detecting ocean plastic pollution through satellite imagery, and recently published their findings in Scientific Reports. First, they obtained high-resolution optical data from the European Space Agency (ESA), which is gathered by the Sentinel-2 Earth observation satellite. Second, they used the plastic target data from the University of the Aegean to help differentiate plastic debris from natural objects like driftwood and seaweed.

Then the researchers employed an algorithm to develop a “floating debris index” (FDI) that would identify macroplastics, like plastic water bottles and plastic bags, bobbing on the surface of the sea.

“I will read an article or a social media post about marine plastic pollution, and then go and look at that area, using Sentinel-2, and process the data using the floating debris index … and then extract those values and feed it into the machine learning algorithm,” Biermann said.

Biermann and her colleagues have tested these methods on satellite imagery of coastal waters off Accra, Ghana; the San Juan Islands, U.S.; Da Nang, Vietnam; and east Scotland, reporting an 86% accuracy rate.

However, the process of identifying plastic isn’t always straightforward. Cloud cover and rough seas can compromise the data, and macroplastics won’t stay in one place for a long time, particularly in coastal zones, Biermann said. “Things change really quickly, so a Sentinel-2 image that I look at today would have been taken two days ago, and by then anything that I see is gone,” she said.

While plastic tends to get pushed around in the ocean, winds and ocean currents will propel it into clusters that stay in one place. Biermann says she hopes that optical satellite data can help identify these aggregates, and that people and organizations can use this information to work on solutions.

“There will be cleanup operations like the Ocean Voyages Institute, which we’d like to work with. They would then go to where we spotted things, and they would be able to remove tons of plastic at a time,” Biermann said. “This really is the first technical exercise, but we would then like to apply the method, far more broadly … to rivers and open waters.”

Biermann makes an important clarification: this satellite data shouldn’t be seen as a solution to the plastic pollution issue.

“On its own, it can’t do anything to curb the plastic pollution problem,” Biermann said. “The way to curb plastic pollution problem is to address the source. We know that the majority of plastics come from land, so it’s not just addressing the source in terms of the industry, but also in terms of waste management practices on land.”

She says she also hopes this data will help build awareness of the global plastic pollution issue, and inspire action on the issue.

“What I don’t want to see is my work being used to greenwash the problem — now we can see it from space, so we know where to go and fetch it,” she said. “That’s not the case at all. And I think if anything, it’s just to say there that there’s enough of it now that it can be seen from space, [and we should] take that message to heart. The individual is not the problem here, and our individual behavior is not generating plastic on such a scale that it can be seen from space. Really, it is an industry problem.”

This article was originally published on Mongabay, written by Elizabeth Claire Alberts, and is republished here as part of an editorial partnership with Earth.Org. 

Through modern innovation in the current age, satellites and space stations are integral for space exploration, scientific discovery, communications, and remote sensing. However, producing and implementing orbital systems is incredibly costly, both financially and environmentally. New technological advancements increasingly require the use of satellites, but with the mounting global ecological crisis, how essential are they?

Over 2 200 active satellites are orbiting Earth, with the US leading with the most satellites per country, followed by China and Russia. In 1966, only six states were participating in the ‘space race’; now, there are 72 countries with active programmes or satellites in orbit. Many satellites are controlled by governing bodies and institutions that cover individual states or trade blocs, such as the National Aeronautics and Space Administration (NASA) in the US and the European Space Agency (ESA), or by national military departments. However, the vast majority of satellites are currently owned and controlled by private firms, an industry that has rapidly expanded in the past decade. The private space sector is experiencing a new uptick in scientific- or business-related endeavours, causing the number of active satellites in orbit to increase by the month. 

Elon Musk, founder and CEO of SpaceX, is launching one such endeavour, called Starlink, a network of low Earth orbit (LEO) satellites that will eventually create a global communications system capable of high-speed broadband internet connections. By the end of 2020, SpaceX is set to launch over 1 400 new satellites to ensure global coverage by 2021, and over 12 000 satellites over the next eight years. Latest reports suggest that number will increase to as many as 42 000 satellites in total, meaning that one single enterprise – SpaceX – will launch and have control of more satellites than have ever been launched since 1957. Starlink purports to be a ‘clean’ satellite constellation, whereby the LEO satellites will de-orbit to keep space clean once their lifespan is complete. However, it is debatable as to how clean the production and launches of thousands of satellites will be in reality. 

SpaceX is not the only new commercial space-venturing company. OneWeb, based in the UK, Blue Origin, founded by Amazon founder, Jeff Bezos, and the Luxembourg-based SES, which is already one of the largest satellite operators in the world, are among many firms looking to the stars to expand into the highly lucrative sector. These enterprises, along with other new government-led and research-based programmes, suggest a recent boom in the space economy that shows little signs of slowing down. Aside from the economic worth of the global satellite industry, which was estimated to be US$360 billion in 2019 (both commercial and government-led), there are many other advantages for society from utilising outer space.

The Role of Satellite in Climate Change

Satellites have a wide range of benefits. However, there are several important uses in the frame of the climate change. From the International Space Station (ISS) to hundreds of other observational satellites, remote sensing allows for climate and environmental monitoring. These imaging satellites are an incredible source of data for climate change research, enabling us to see the global changes on the planet that are happening more frequently, and with data freely available for anyone to view and use. For example, changing oceanic temperatures, currents and rising sea levels can be monitored by space-based research instruments. ISS measurements have indicated that global sea levels have increased by an average of 3.3 millimetres per year since 1993, due to melting glaciers and sea ice, and from thermal expansion within the oceans. Additionally, satellite imagery can show the changing sizes of glaciers and sea ice, which show that after 2017, 2019 had the second-lowest sea ice extent in the Arctic since 1978, with a similar situation in the Antarctic’s sea ice extent and coverage.

Outside Looking In: Satellites in the Climate Crisis
NASA Satellite images of the sea ice extent changes between 1979 and 2015 in the Arctic, showing a massive decline as a result of climate change and anthropocentric activities around the globe (Source: NASA

Remote sensing satellites, such as NASA’s Global Precipitation Measurement (GPM) satellite, can determine the changing precipitation patterns and flooding. Rainfall changes indicate that globally, more extreme weather events are happening, with more droughts, flooding and hurricanes. Vegetation cover changes are also observable, even with the naked eye from space. Along with NASA’s GPM, ESA’s Copernicus Sentinel-2 satellite enables spatial mapping of biodiversity and biomass, agricultural impacts, soil degradation, forestry cover and deforestation (and afforestation). Understanding this is essential for understanding the bigger picture for better ground-level mitigation and management of degradative land uses, such as intensive agricultural practices.

Observations of how widespread wildfires have been would not have been possible without a satellite’s viewpoint, showing worsened conditions of increasing fire risk, frequency, and magnitude as a result of climate change, which also feedbacks to increase carbon dioxide emissions. In the recent (and ongoing) Australian bushfire crisis, satellite imagery has shown the extent of burnt land in the country, and the distance the smoke travelled at the peak of the fire season, reaching as far away as South America. More recently, satellite images have shown that nitrogen GHGs have dropped in areas affected by COVID-19 quarantine measures, such as in China and Italy.

Greenhouse gases (GHGs) and temperature changes are also monitored from satellites, making them essential in modelling past, present and future differences to understand the atmospheric, terrestrial and oceanic implications from climate change. Instruments such as NASA’s Atmospheric Infrared Sounder (AIRS) satellite can measure GHG increases, such as CO2. Carbon dioxide levels are regularly monitored from space, showing that atmospheric CO2 levels have reached 413 parts per million (ppm). This is the highest concentration of CO2 that our planet has experienced in 3 million years. Satellites can also detect other GHGs, such as methane and nitrous oxide, which often come from industrial leaks or oil and gas fields. Satellites are integral for compliance with international environmental treaties such as the Paris Agreement. In aiming to keep within the Agreement’s target of mitigating global warming to 1.5°C above pre-industrial temperatures by the end of the century, satellites show we are already at 0.98°C above, a number that fluctuates annually.

Aside from the fundamental need to understand climatic changes from space, satellites are useful for early warning systems for natural disasters, the increased occurrences of extreme weather events, or ‘human disasters’. Satellites can monitor weather events in case of necessary evacuations, such as hurricane or flooding events, which are usually in conjunction with land-based monitoring systems and institutions (e.g. National Oceanic and Atmospheric Administration (NOAA) in the US). For natural disasters such as earthquakes, tsunamis or landslides, satellites are just as important in answering disaster events. Satellites have even been able to detect minute changes in human-made infrastructures, such as monitoring changes in road surfaces before a bridge collapse.  

However, despite the array of advantages of satellites in the climate crisis, what are the implications and costs of utilising the space beyond our immediate atmosphere?

Space exploration and entrepreneurship are very costly ventures. Sourcing the parts for satellites is expensive due to the amount of rare and valuable materials within them; production, engineering and software costs are similarly very high, often upward of US$100 million per satellite. Consequently, only states, companies, and individuals with significant disposable capital (or those with sponsorship from state or private funds) can viably finance space programmes. As a result, there is a disproportionate allocation of control over space from entities and institutions that can financially support such ventures, prohibiting many countries from accessing the benefits of satellite control. 

The pollution crisis of the Earth’s waterways is well-documented. This notion is reflected beyond our atmosphere. Space debris is an issue that is not often talked about; apart from the International Space Station (ISS), most people will never have contact with outer space, and therefore it is not often an immediate concern. 

Old shuttles and satellite parts enter the planet’s atmosphere on a reasonably regular basis, estimated at 200-400 pieces a year. While these parts frequently burn up upon re-entry and have minimal direct impact on terrestrial regions, they do not disappear completely. By burning up, due to the intense friction of travelling from a vacuum to an atmosphere full of gases, noxious chemicals and GHGs are released in the upper atmosphere. These gases, while negligible in amount, are generally more potent than CO2, and can deplete the ozone layer or retain more thermal radiation. 

Estimates by ESA put the number of space junk objects in Earth’s orbit at approximately 900 000 objects over 1cm in size, of which around 5 400 of those are larger than one metre (including over 2 000 active satellites). Roughly 70% of these pieces are in LEO. Space debris can be anything from bolts, paint chips and instrument parts, to entire defunct satellites and rocket bodies. Any object 10cm in size or larger can have a significant effect on active spacecraft due to the high speeds that objects orbit at; most modern satellites and stations are fitted with debris shields for smaller pieces. 

Outside Looking In: Satellites in the Climate Crisis
Space junk image projection by ESA, of pieces larger than 1mm in size in Earth’s orbit (Source: ESA).

Historically, space junk has destroyed active satellites, creating more debris in the process. In the future, a chain reaction of colliding space debris, known as the Kessler syndrome, could render LEO unusable. Such a reaction could inhibit the possibility of communication and essential remote sensing satellites that many people and organisations around the world rely on every day. It could also dissuade future space programmes from taking place due to the threat of extra-terrestrial debris. The implications of adding Starlink’s potential 42 000 new space instruments into orbit over the next decade or so, not to mention others, are innumerable in terms of impacting the already-fragile environment.

More positively, there have been several operations seeking to remove such debris from space. In 2018, British satellite RemoveDEBRIS was launched and deployed from the ISS to test new technologies that were successful in capturing space debris. Alternatively, another way to mitigate space debris in altitudes where satellites typically orbit is to move them to a ‘graveyard orbit’, where instruments near the end of their lifespan are sent to altitudes of 225 miles from Earth’s surface and higher, although this does not entirely solve the space junk crisis.

Unsurprisingly, the requirements for constructing a satellite make them incredibly resource-intensive. An immense array of elements and raw materials are used to create space structures; kevlar, aluminium, silicon, titanium or composite alloys such as nickel-cadmium and aluminium-beryllium are often essential. This is without considering the many resources necessary for electrical systems onboard the satellite, and the methods of building the space-faring instruments. The mining of metals alone is highly energy-intensive and degradative to the surrounding environment, including atmospheric and groundwater pollution. Following extraction, deoxidation or purification of the resources also contribute to the total emissions, along with transportation of the materials to production facilities. 

The effects of launch emissions from solid rocket fuel are not well understood and are difficult to measure. The majority of satellite launches produce a negligible amount of CO2, especially in comparison to other industries. However, particulates produced in the launch interact in the stratosphere and have a significant impact on ozone depletion. For instance, alumina particles are emitted from the launch and absorb sunlight, enabling thermal heating in the upper stratosphere and causing positive feedback and further latent warming. The effects of other gases and particles’ interactions with upper atmospheric environs have yet to be modelled, meaning every new rocket launch has unknown and potentially critical implications for climate change. 

Some reports state that liquid hydrogen, an alternative rocket fuel to solid propellants, is almost carbon neutral with 28 tons of CO2 per launch, alongside water vapour. However, the impacts of initially creating the specialised liquid fuel are estimated to be upward of 672 tons of CO2 per launch due to the industrial-scale amount of energy needed to produce the fuel, meaning the supposedly ‘clean’ fuel type is not as green when taken at face value. Ironically, satellite imaging will likely be the most effective tool in understanding the upper atmosphere’s composition and the impact of space programmes’ launch emissions on the atmosphere. 

Satellites are incredibly important in understanding and combating climate change. Understanding the climate crisis and its related issues are integral to combating it- if we cannot measure it, we cannot mitigate it. Without satellite capabilities, the knowledge and data on global warming and climate change today would not be anywhere as close to what we have available now, even with land-based sensing equipment. Nevertheless, there are implications and costs associated with satellites. When considering the Starlink programme, the overall impacts caused by one single private firm will be vast. There will be knock-on effects well into the future, such as production pollution, launch emissions from tens of thousands of satellites, and space debris. It is debatable as to how necessary a slightly higher coverage and faster internet speed will be in light of the ever-imminent climate crisis. 

With the onset of a ‘new space race’, policymakers need to be taking a serious look at the environmental costs of satellite use and improving research capabilities and regulation in order to mitigate these degradative implications. Future programmes need to invest in reducing or offsetting emissions and taking more responsibility for satellites once they have reached the end of their life. In the case of active satellites, retrofitting them to be less resource- or emission-intensive could be a viable solution in aiding this, depending on future technological and engineering advancements.

Earth.Org analysed satellite data to assess the concentration of methane emissions in the Greenland ice sheet (GiS) in July 2019. The GiS covers an area of roughly 1,7million square km; together with Antarctica’s ice sheet, it contains more than 99% of the world’s fresh water. Most of this water is frozen in masses of snow and ice and as greenhouse gases build, the oceans absorb 93% of the excess heat those gases trap. The warming air and water are causing ice sheets to melt at unprecedented rates. 

Besides sea-level rising, the melting of this ice sheet in Greenland has another side-effect- methane emissions, which has rapidly increased in the past decades and more than doubled from pre-industrial times.

Methane, or CH4, has a 20-year Global Warming Potential (GWP) of 84, which means that over a 20-year time period, it’s 84 times more powerful than CO2 at trapping heat in the atmosphere. Methane emissions are temperature-sensitive and could provide significant feedback mechanisms in a changing climate. 

Arctic Methane

The Arctic region is one of the most abundant natural sources of methane. It is estimated that the Arctic permafrost (carbon-rich soils that remain completely frozen for at least two years straight) stores 1 650 gigatonnes of organic carbon, twice the amount of greenhouse gases in the atmosphere. 

As the temperature rises above 0°C, microbes in the permafrost decompose frozen organic matter into methane, an anaerobic biotic process known as methanogenesis. Thawing of the permafrost produces both methane and CO2. A warming climate can induce environmental changes that accelerate this decomposition and release of greenhouse gases. This feedback can accelerate climate change, but the magnitude and timing of greenhouse gas emissions from these regions and their impact on climate change remain unclear. This makes it all the more concerning that ice sheets are currently ignored in global methane budgets and that there is no existing data on the current methane footprint of ice sheets. 

A study conducted by the University of Bristol found that much of the methane produced beneath the ice likely escapes the GiS in large, fast flowing rivers before it can be oxidised to CO2

A study estimated that 6.3 tonnes of methane was transported by meltwater underneath the ice in the summer of 2015. Every summer, the ice sheets melt in Greenland, peaking in June to August and although this is a natural process, global warming is accelerating the rate of melting. Subglacially produced methane is rapidly driven to the ice margin by the efficient drainage system of a subglacial catchment of the GiS. Another study reported a concentration of methane emissions 15 times the background atmospheric concentration in the air expelled with meltwater in West Greenland in 2016. The total amount of methane released with meltwater remains unestimated.

From 1992 to 2018, about half of the ice loss from Greenland was from melting driven by air surface temperatures, which have risen much faster in the Arctic than the global average (more than double), and the rest was from the speeding up of the flow of ice into the sea from glaciers, driven by the warming ocean. 

The Sentinel- 5P satellite captures methane hot spots where methane-saturated fluxes reach the ice margin. 

While many studies place their focus on the West GiS, the satellite images produced from Sentinel- 5P have revealed another bright hot spot on the north, near the North Pole. 

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Satellite Image of Methane Emissions in Greenland

The image above shows the concentration of methane in Greenland in July 2019 according to images taken by Earth.Org from the Sentinel- 5P satellite. The mean methane concentration over Greenland during the month was 1 809.6 ppb (parts per billion), with a local maximum of 1 968.2 ppb. 

The information for the images above is taken from research by the National Snow and Ice Data Center, which Earth.Org has tabulated. The top graph shows the mean daily melting area during melting seasons from 1981 to 2019, and the bottom graph shows the maximum daily melting area during melting seasons from 1981 to 2019. 

Researchers suggest that the microbes in the frozen soil contain methane-oxidising communities, essentially making the tundra a methane sink. The effect of methane digestion increases with temperature, so it is particularly potent in the growing seasons (July- September).

Studies suggest that a longer growing season results in ‘potentially high emissions’ by permafrost systems. This creates a cycle, called a ‘climate change feedback’, whereby global warming causes ice sheets to melt, which releases more methane, which in turn exacerbates global warming. 

Greenland Ice Melt

According to a study conducted in December, Greenland’s ice is melting seven times faster than it did in 1992. From July 30 to August 3, melting occurred across 90% of the continent’s surface, dumping 55 billion tonnes of water over 5 days. On August 1, the GiS lost 12.5 billion tonnes of ice, more than any day since researchers started recording ice loss in 1950. 

Melting seen at this rate was not expected for another 50 years; by the last week of July, melting had reached levels that scientists with the IPCC had projected for the year 2070 in the most pessimistic scenario. 

The region has lost more than 4.2 trillion tonnes of ice in the last 25 years, which has raised global sea levels over 1cm. The rate of ice loss has risen from 33 billion tonnes a year in the 1990s to 254 billion tonnes a year in the last decade. The IPCC has estimated that global sea levels could rise by 60cm by 2100, putting 360 million people at risk of annual coastal flooding. However, this new study shows that if the current melt rate continues, Greenland will raise sea levels nearly 7cm more than the IPCC’s prediction by 2100, putting an additional 40 million people at risk. 

One of the keys to reducing methane emissions in Greenland, and certainly the rest of the world, is cutting the use of fossil fuels. Additionally, there is too much uncertainty surrounding the impacts of these environments on the planet and they should be considered in the Earth’s methane budget so as to allow researchers and policy makers to collaborate to mitigate and manage the effects of these emissions. 

This is the second of two parts in an Earth.Org investigation of methane emissions in the polar regions. See December 20th’s article, ‘Methane Emissions in the Arctic Could Amplify Global Warming’. 

Featured image by: Christine Zenino

Unlike other satellites, PRISMA can read the chemical composition of ground and water based on light refraction. 

The first images captured by PRISMA Earth observation satellite of the Italian Space Agency (ASI) reveal the quality of water in various lakes in Italy. PRISMA mapped the lakes measuring the Nephelometric Turbidity Unit (NTU) of the waters, which assessed to be varying in different areas.

What is PRISMA?

Launched in orbit on March 22 this year with a powerful hyperspectral optical sensor, PRISMA is a first-of-its-kind earth observation tool designed to provide information about environmental monitoring, natural resource management, pollution, and crop health. 

Mapping Lake Trasimeno, the largest lake in Central Italy, PRISMA inferred that the waters are generally less turbid in the south-eastern bay, where communities of aquatic macrophytes thrive on a large scale. Macrophytes have the ability to limit resuspension of bottom sediments in a waterbody. 

Italian National Research Council (CNR-Irea) officials stated that further data processing would reveal in-depth details about the terrestrial ecosystem of Italy and other parts of Europe.

PRISMA operates in a Sun-synchronous orbit, which enables it to circle the Earth in such a way that the Sun is always in the same position as the satellite takes pictures of the planet below.

From its orbit, at about 620 kilometers of altitude, PRISMA (an Italian acronym for Hyperspectral Precursor of the Application Mission) observes the Earth on a global scale with different eyes. It includes a medium resolution camera that can view across all visual wavelengths and a hyperspectral imager that can capture a wider range of wavelengths between 400 and 2500 nanometers.

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The satellite image of Lake Trasimeno shows a turbidity gradient that varies between 3 and 6.2 NTU

“It will be able to offer an unprecedented contribution to the observation of natural resources from space and to the study of main environmental processes,” said an official release from the Italian Space Agency. “It studies the interactions between atmosphere, biosphere, and hydrosphere. It also tracks environmental and climate changes on a global level; the aftermath of anthropic activities on ecosystems.”

Why is PRISMA important?

PRISMA is able to provide valuable information to support the prevention of natural hazards like floods and man-made quandaries like soil pollution. It can also monitor fixed objects and protected areas of cultural or environmental significance, aids actions to humanitarian crises, and explores mineral resources. 

“Unlike the passive satellite sensors currently operating, which record the solar radiation reflected by our planet in a limited number of spectral bands, PRISMA will be able to acquire 240 spectral bands,” said the ISA statement. “This will help us to refine our knowledge concerning natural resources and climate change.”

PRISMA was developed by a consortium led by OHB Italy and Leonardo. 

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